In many types of motor vehicles it is desirable to provide speed governing to ensure that the road speed does not go above a predetermined limit and that the engine speed is allowed to made only brief excursions above its predetermined limit. The governing system should not unnecessarily restrict either the engine speed or the vehicle speed. Governing systems of this type are known to improve the economy of vehicle operation by reducing fuel comsumption and engine maintenance costs and increased operating life. Further, such systems afford the vehicle driver the convenience of operating the vehicle with a fully depressed throttle to maintain a cruising speed.
It is also desirable to provide an engine and load speed governor which can be installed as an add-on unit either in the factory or in the field without the cost and inconvenience of replacing or modifying the carburetor, ignition system and speedometer cable of the vehicle.
Engine and load speed governors of this general type are known in the prior art. The Sturdy U.S. Pat. No. 4,181,103 discloses a governor of this type which is characterized as a dynamically-surging governor which allows engine speed to oscillate rapidly about its predetermined limit when the vehicle is operated in a lower gear ratio. In the governor of this patent, the throttle limit is driven over a wide range between wide open and the fully closed positions when a predetermined speed is reached.
The governor disclosed in my co-pending application Ser. No. 168,566 allows the engine to be accelerated to its predetermined limit with small overshoot and then it regulates the speed in close approximation to the predetermined speed limit. In this governor, the engine throttle limit is positioned at a reference position, between wide open and close throttle position, when the engine reaches a predetermined speed. In this system, the overriding throttle closing means moves at the relatively fast rate during movement outside a reference zone and at a relatively slow rate within the reference zone.
Electronic control circuits especially adapted for use with governors of the type are disclosed in Kasiewicz U.S. Pat. Nos. 4,090,480, 4,257,136 and Ser. No. 167,964.